1. Field of the Invention
The present invention relates to a terminal box used for a solar cell module.
2. Description of the Related Art
A conventional terminal box includes a main body containing: at least one pair of terminal strips which are connectable to a positive electrode and a negative electrode of a solar cell module; and a backflow prevention diode bridged between the terminal strips to connect the terminal strips. In this type of the terminal box, a pair of the planar terminal strips are arranged in parallel at a distance, the backflow prevention diode is bridged between the terminal strips in such a manner that a lead wire of the backflow prevention diode is placed across a full width of the corresponding terminal strip, and the lead wire is soldered (see, for example, Japanese Utility Model Registration No. 3069523).
In the conventional terminal box described above, the lead wire of the backflow prevention diode is soldered while the lead wire is placed on the planar terminal strip, and thus the solder is likely to spread to other parts along a plane of the terminal strip, and heat of the spread solder may involve a risk of an adverse influence on other parts (e.g. devices). In addition, if the solder spreads to other parts and an amount of the solder becomes insufficient for an essential portion of the lead wire, there is a risk of lowering in a fixing strength. In other words, there is a problem that fixing of the backflow prevention diode is likely to become unstable.
Another conventional terminal box includes: at least one pair of terminal parts which are provided in a main body and connectable to a positive electrode and a negative electrode of a solar cell module; at least one pair of connection parts which are provided on one lateral face of the main body and each of which is configured to conductively connect an external cable to the terminal part; and an adhesive surface which is provided on a rear face of the main body and adhesive to the solar cell module. In this type of the terminal box, the main body has a cuboid shape, one of whose four lateral faces is provided with a connection part, with each of the other three lateral faces being in a shape of a planar wall (see, for example, Japanese Unexamined Patent Application Publication No. 2006-339659). In addition, a rear face as bottom of the main body is configured so that an entire surface constitutes an adhesive surface to which an adhesive is applied.
In the conventional terminal box described above, if an external force acts on an external cable connected to the connection part in a direction to remove the terminal box from an attaching face of the solar cell module (hereinbelow, referred to as “removing direction”), there may be cases where the adhesive surface is peeled off and the terminal box is detached. A relationship between an external force P and an adhesive force (resultant force) J in this case is represented in the drawing of FIG. 9A. Specifically, on a connection part 208 provided on one lateral face B3 of a main body 201, the external force P in the removing direction acts, and on an adhesive surface 207, the adhesive force J acts as a drag. Since the external force P and the adhesive force J are different in their point of actions, these forces act as a couple of forces. As a result, a rotational moment in which the other lateral face B4 of the main body 201 serves as a rotational center acts on the main body 201.
The reference character “Lp” in the drawing indicates a distance from the rotational center to a point on which the external force P acts. The reference character “Lj” in the drawing indicates a distance from the rotational center to a point on which the adhesive force J acts. The following relationship is obtained: Lp=(Lj×2).
Therefore, in order to prevent the terminal box from being removed which may otherwise be caused by the action of the external force P, a balancing relational expression of (Lj×J)>(Lp×P) should be met. In other words, an adhesive material should be upgraded to one with a higher adhesion strength.
For a terminal box in which a bottom wall of a main body is provided with a terminal strip to which an output terminal of a solar cell module and a core of a power cable are connected, Japanese Unexamined Patent Application Publication No. 11-26035 describes that the terminal strip is disposed inside the main body, the power cable (output cable in the document) is inserted into the main body and the core of the power cable is swaged by a swaging part of the terminal strip, to thereby electrically connect the power cable and the terminal strip. The document also describes that a lead wire of a bypass diode is soldered to a projection piece of each of a pair of the terminal strips, and the output terminal (lead wire in the document) of the solar cell module is soldered to a leg part of the terminal strip.
Japanese Unexamined Patent Application Publication No. 11-26035 further describes that an engaging hole is formed in the terminal strip, an engaging projection of the main body is inserted into the engaging hole so that the engaging projection protrudes from the engaging hole, and the protruding portion is melted using ultrasonic wave to make a diameter larger and then cured, to thereby fix the terminal strip to the bottom wall of the main body.
As described above, the terminal box used for the solar cell module requires works to connect the output terminal of the solar cell module and the power cable to the terminal strip, when the solar cell module is installed. As a result, more efforts are required, and thus improvement in workability has been demanded.
Considering a mode of work upon inserting the power cable into the main body, a coating of the power cable is removed to expose the core which is then inserted into a hole or the like of the main body. Since thin wire rods are used for the core, they are likely to be bent. Consequently, when the core is inserted into a hole or the like, the core frequently comes into contact with a wall face inside the main body, a rib or the like, and a smooth insertion is hindered. Especially, when the core comes into contact with an interior of the main body, there may be cases where a bundle of the wire rods spread (unravel), and thus there is a room for improvement.
For a terminal box including: a main body containing a terminal strip configured to electrically connect an output terminal of a solar cell module and a power cable; and a lid for closing an opening of the main body, Japanese Unexamined Patent Application Publication No. 2003-197944 describes a configuration in which a terminal strip (electrode connection terminal in the document) is provided on a bottom wall of a main body (terminal box in the document), a lid is provided for closing an opening of the main body, a sealing groove is formed along a peripheral wall surrounding the opening of the main body, and a sealing member is provided in the sealing groove.
Japanese Unexamined Patent Application Publication No. 2003-197944 describes a configuration in which a mounting part for lid as an engagement recess is formed in the peripheral wall surrounding the opening of the main body, while the lid is provided with an engagement projection. Due to this configuration, when the opening of the main body is closed with the lid, the engagement projection of the lid engages with the engagement recess of the mounting part and a closed state is retained. At the same time, the sealing member is brought into contact with an inner face of the lid to create a sealed state. When this lid is removed, maintenance and inspection, or repair of failures, can be performed.
Japanese Unexamined Patent Application Publication No. 2003-197944 also describes a configuration in which, while the power cable (connection cable in the document) is inserted into the main body, the lid is attached to the main body, and the core of the power cable is brought into contact with the terminal strip by a pressure of a pressing part of the lid.
As described in Japanese Unexamined Patent Application Publication No. 2003-197944, the terminal box is often used in a state in which it is brought into close contact with a rear face or the like of the solar cell module, and for the purpose of preventing rain water and dust from entering the terminal box, a high sealability is demanded in the closed lid. In addition, for maintenance and inspection or repair of failures, the lid should be removed.
However, as described in Japanese Unexamined Patent Application Publication No. 2003-197944, in the case of the terminal box in which the lid is completely fitted with the main body to keep the closed state, when an internal pressure of the main body is increased, for example, along with the temperature increase, it becomes difficult to discharge air inside. Accordingly, the terminal box or the lid may be deformed.
An object of the present invention is to provide a terminal box that solves the above-mentioned problems and ensures the fixing of the backflow prevention diode to the terminal strip.
Another object of the present invention is to provide a terminal box that solves the above-mentioned problems and is unlikely to be removed without using an upgraded adhesive material.
Still another object of the present invention is to provide a reasonably configured terminal box in which work of connecting the power cable to the terminal strip is facilitated.
A further object of the present invention is to reasonably configure a terminal box in which the internal pressure of the main body can be released while the sealability of the main body is retained.